If A Cannonbal Was Fired Verticaly From A Moving Train

[jolly geoff]

where would it land ,behind,infront or on the train

[pixie374]

It depends how long the train is too. If I threw a ball straight up in the air and stepped left, it would land next to me. Why would this be different?

[ToraToraTora]

gawd elp us!

[Prudie]

Why do people have to get so snotty on these kind of posts. Anyway so today I have learned that absolutely anything fired at absolute vertical from a moving train, irrelevant of the force behind it or how high in the sky it travels it will land back on the train. Interesting.

[jolly geoff]

wrong prudie it would land behined the train, air ressistance would slow the objects forward motion down

[ToraToraTora]

This is a classic einstienian thought experiment. Meant to illustrate, in this case relative motion. In order to focus on the point we must disregard day to day inhibiting factors that effect the outcome that is trying to be illustrated. Eg if the train was going at 1000mph and the cannon fired the ball at 40000mph then the ball would reach escape velocity and never come down. BUT we are not trying to demostrate the obvious, we are trying to show that then a ball direct directly up on a moving train traces and arc back into the cannon.

[Prudie]

What do you mean wrong? that's what everyone has answered to you

[ToraToraTora]

we should ignore air resistance for the purpose of this thought experiment but in the case of a cannon ball I doubt it would have much effect, it would probably hit the lip of the cannon but that's not what we are discussing. Eg when Galileo attempted to demonstrate that that different weight objects fall at the same rate he dropped different weight cannon balls of metal wood etc off the Tower of pisa. Only later was it confirmed by David Scott on the moon. Galileo and latterly many others knew what would happen but the atmosphere prevented a demonstration on Earth. In order to grasp the point we here must exclude the atmosphere.

[vascop]

For once I agree with Nigel Farage: If we ignore air resistance and assume that the train continues at the same speed, then the canon ball will come back into the cannon.

[vascop]

Sorry meant to write "cannonball" not canon ball!

[douglas9401]

If we keep ignoring stuff then it could land in my back garden.

Hopefully missing the greenhouse.

[Old_Geezer]

Does it achieve escape velocity ?

[Zacs-Master]

So that’s that then. It would land behind the train in Dooogie’s back garden, narrowly avoiding his greenhouse but possibly bruising his cotoneasters. Marvellous.

[Rev. Green]

You are all wrong. It would land at the side of the train! Okay, I'm assuming the train line runs roughly North/South and it's a mighty powerful cannon. (Coriolis effect)

[Old_Geezer]

Ah... but what if the train is running on a curved track ?

[Hopkirk]

How on earth can you ignore wind resistance?

Stick your head out of a speeding train, and it's pretty hard to ignore.

[jim360]

"How can you ignore wind resistance??"

It makes the problem easier :P

[douglas9401]

"How on earth can you ignore wind resistance?"

Simply adopt that old Borg saying.

[sunny-dave]

Or indeed Dalek - “Resistance is useless “ ...